Preheat your oven to 350 degrees. Grease a 9-inch pie dish with cooking spray and set aside.
Add all dry ingredients: sugar, flour, cinnamon, and salt to a large bowl and whisk together until just combined.
Melt the butter in a medium microwavable bowl and let it cool slightly then add eggs, vanilla to the bowl and whisk all together.
Pour the wet ingredients into the dry and mix to combine to create the cake batter, but do not over mix.
Add the 2 cups of fresh blueberries and carefully fold them into the cake batter. The batter will be very thick.
Use a spatula to scrape the batter out of the bowl and into your greased pie dish and smooth out the top.
Sprinkle ¼ cups of blueberries on top and lightly press in.
Bake for 30-35 minutes or until the middle is set and edges are a bit crisp and a toothpick comes out clean from the center.
Allow pie to cool in the dish and dust with powdered sugar or skip right to serving it warm with ice cream or cool whip!